When a person's jaws, teeth, or facial muscles do not develop normally, various type misfits or malocclusions occur between the upper and lower jaws and/or the individual teeth of the upper and lower arches of teeth. Three common types of malocclusions as categorized by orthodontists are described as follows: Class I--The jaw relation is normal but individual teeth in the upper or lower arch are not growing in ways to achieve a good fit with their corresponding teeth in the opposite arch. This malocclusion of the teeth is commonly corrected by the installation of braces to move or straighten the misdirected teeth; Class II--Wherein the lower jaw is not growing downward and forward in a normal manner along an imaginary sloping line from the ear to the person's lower jaw which has been called the Y axis of growth by orthodontists. In such cases, the upper and lower arches of teeth do not fit properly, and the fit or bite of the teeth occurs between the wrong teeth in the upper and lower arch. This condition, called an overbite, is commonly corrected by moving the lower jaw forward by some means so that the proper teeth of the upper and lower arch meet each other when the jaws are closed or by moving the upper jaw back. Treatment requires that the jaw be held in the new proper bite position so that the jawbones and muscles will grow in ways which support this new bite; Class III--Wherein the lower jaw has grown forward so far that when the mouth is closed, the upper arch of teeth sets down behind the lower arch of teeth. This condition is called underbite and is commonly corrected either with the use of braces with rubber bands or by surgery wherein portions of the rear lower jaw are removed and re-aligned so that the upper arch of teeth sit properly ahead of the lower arch when the jaws were closed. A complication of underbite or Class III type problems is that since the lower jaw has in a sense gotten ahead of the upper jaw, the growth of the lower jaw does not push forward the growth of the upper jaw and the facial muscles are not properly developed. If left untreated, the condition worsens as the lower jaw protrudes further and the upper jaw and its muscles remain undeveloped. This condition creates a sunken facial profile.
Orthodontists have previously used several types of appliances to correct each of the three major classes of orthodontic problems.
Braces are generally appliances for the correction of many types of orthodontic problems, particularly Class I problems. However, they have no direct effect on the bite problems of Class II or Class III patients. To correct the bite, one must put pressure on or link together the entire arch of teeth or the jaws of the patient. As the braces are normally in place to correct tooth alignment problems, they provide a convenient point of attachment for a myriad of bite correcting appliances from head gears to rubber bands.
Ideally, the patient may use braces and a bite correcting device at the same time. In this way, the entire malocclusion of teeth and jaws can be simultaneously corrected. Some appliances preclude the use of braces and require two separate phases of treatment, one to correct the alignment of the jaws and one to correct the alignment and fit of the teeth. The problem with orthodontic appliances heretofore used was that almost all of them were removable by the patient and thus were ineffective or unpredictable in treatment results.
One type of orthodontic appliance used with braces and generally termed elastics or rubber bands, has been used to treat Class I, Class II, and Class III problems. Such appliances come in different sizes and strengths and are used to create a pull-type pressure between two points in the patient's mouth. They are usually attached to normal braces and are used intermaxillary (between two jaws) and intramaxillary (same jaw) as required, having the advantages of being removable for chewing and brushing and also being disposable and therefore easily replaced rather than cleaned. In use, they exert only light forces in the two to eight ounce range, thereby not damaging braces.
However, a serious disadvantage with elastics is that they are removable by the patient, who often forgets to replace them after eating. This greatly reduces the effectiveness of the treatment which is dependent on consistent application and thus the cooperation of the patient. When the patient fails to keep the elastics properly attached, the treatment is not only retarded but in some instances other pressures set on braces can undo the gains made when the elastics were attached. An additional disadvantage is that the elastics stretch and weaken after use and thus fail to provide a steady or consistent amount of force during the period of use. Finally, the force exerted by elastics is a pull-type force which creates a straight line of tension between two points. Thus, when elastics are attached between the upper and lower jaw to treat an overbite condition, they pull the jaws together at an angle which is almost perpendicular to the natural angle of growth along the Y axis. This indirect use of force to encourage the lower jaw to grow forward and downward in Class II type problems requires much more time than a more direct use of force to push the lower jaw forward along the Y axis.
Several attempts have been made to replace elastics with small springs which pull the jaws together, as for example in the patent to Armstrong U.S. Pat. No. 3,618,214 which uses springs inside plastic tubes. This device operates in the pull mode like an elastic. However, it offers none of the advantages of the elastic and suffers from all the disadvantages plus the additional disadvantage of being obviously uncomfortable for the patient. Another attempt to solve the overbite problem with an elastic type device is disclosed in the patent to Nelson U.S. Pat. No. 4,074,433 which utilizes a pull cable retained by spring loaded anchor elements. However, this device not only has the inherent limitations of conventional elastics but would obviously be more difficult to install, adjust, and keep clean.
Functional appliances have also been used to treat bite problems. These utilize molded pieces of plastic and wire which work something like the mouth piece used by boxers. In place, such an appliance exerts light forces in the mouth in the very low range of zero to 1/4 ounce and can achieve favorable results when used consistently by the patient. However, a serious disadvantage with such devices is that they are removable, easily taken out, often lost and easily broken. Also, a patient cannot use the mouth to eat or brush while such molded devices are in normal position. Therefore functional appliances have proven to be generally unpredictable in treating an bite problems because most patients find them too inconvenient for regular use and cosmetically unpleasant.
Still another appliance which has been used to counteract and overcome an overbite condition is a headband which is attached to the braces. Rather than pushing the lower jaw forward, it works by pulling the upper jaw back. To do this, such appliances use one to two pounds of force, which is the maximum which can be tolerated by braces. The head gears have the same advantages and disadvantages as the functional appliances. They are obviously cosmetically undesirable.
In the early 1900's a Dr. Herbst, in Germany, developed an appliance which pressured the lower jaw forward to accelerate its growth in order to treat an overbite condition. This was the first fixed or non-removable bite correcting appliance. The Herbst device used rigid steel bars or rods which, once installed, could not be removed by the patient. However, the normal biting force exerted by the jaws of a patient and transmitted by the rigid bars required the placement of a heavy metal reinforced plastic overlay over the upper and lower teeth or the placement of steel crowns on the teeth. The rigid bars and the overlay support made eating extremely difficult for a patient and created severe oral hygiene problems as well as cosmetic problems. Moreover, the rigidity and lack of flexible connections for the Herbst links transmitted such large force components (18-30 lbs.) that damage to the appliance or braces thereon often resulted.
Despite the aforesaid drawbacks and problems, Herbst and Herbst-like appliances have been used, as shown by the patents to Northcutt U.S. Pat. No. 3,798,773 and Mason U.S. Pat. No. 4,551,095. In both Northcutt and Mason, the rigid steel bar links attached to an associated heavy metal reinforced plastic overlay are replaced by a system of rigid telescoped tubes attached to the arch wires of braces. These appliances are attached to the arch wire of braces by relatively complicated connecting devices that allow for limited movement. Thus, the rigid bar links, as with earlier Herbst devices, not only tend to exert excessive forces at their attachment points but also cannot be moved aside by the patient for chewing, speaking, and hygiene.
It is therefore a general object of the present invention to provide an improved orthodontic appliance for treating patients with an overbite or underbite malocclusion that overcomes the aforesaid problems of prior art devices.
Another object of the invention it to provide an orthodontic appliance for treating an overbite condition that can be worn constantly during a prolonged treatment period and will bend upwardly or downwardly when necessary to allow the patient to talk, chew and maintain proper oral hygiene with the appliance installed.
Another object of the invention is to provide an orthodontic appliance for correcting an overbite condition that is relatively easy to install in a patient's mouth and also relatively easy to adjust so that a proper amount of push force will be applied to make the treatment effective.
Another object of the invention is to provide an orthodontic appliance for treating an overbite condition that has a degree of flexibility and movement and thereby eliminates the problem of creating excessive stresses at attachment points within the patient's mouth.
Yet another object of the invention is to provide an orthodontic appliance that can be installed and used with equal effectiveness whether or not the patient is wearing braces.
Still another object of the invention is to provide an orthodontic appliance that is cosmetically acceptable because it requires no external component outside the mouth that can be seen.